Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare destructiveHint=true and readOnlyHint=false. The description adds valuable behavioral context by restricting deletion to draft invoices that have never been sent, and it warns against using this tool for sent invoices. This goes beyond the annotations and gives the agent a fuller picture of the tool's safety boundaries.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is very concise—two short sentences. It leads with the action, then states the condition and alternative. Every word earns its place, with no filler or redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple one-parameter tool with a clear annotation (destructiveHint) and an output schema, the description is fully complete. It states what the tool does, when it is appropriate, and what to use instead. No additional context is needed.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% (the single parameter 'invoiceId' has a description 'Invoice ID to delete'), so the schema already documents the parameter fully. The description adds little about the parameter format or usage, which is acceptable given the high schema coverage. Baseline of 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a clear verb and resource: 'Delete a DRAFT invoice.' It specifies the exact target (draft invoices) and distinguishes from the sibling tool void_invoice by stating the condition for deletion (never sent). This makes the tool's purpose unambiguous and differentiates it from similar tools.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly states when the tool should be used ('Only invoices that have never been sent can be deleted') and provides a direct alternative for other cases ('otherwise use void_invoice'). This is strong usage guidance, giving the agent clear decision criteria.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.